Watch and Clock Escapements eBook

The intersection of the line B e with the arc
h, which we will term the point n, represents
the location of the inner angle of the exit pallet.
We have already explained how we located the position
of the outer angle at o. We draw the line
n o and define the impulse face of the exit
pallet. If we mentally analyze the problem in
hand, we will see that as the exit pallet vibrates
through its ten degrees of arc the line B d
and B c change places, and the tooth D’’
locks one and a half degrees. To delineate the
locking face of the exit pallet, we erect a perpendicular
to the line B e from the point n, as
shown by the line n p.

From n as a center we sweep the short arc t
t, and from its intersection with the line n
p we lay off twelve degrees, and through the point
so established we draw the line n u, which defines
the locking face of the exit pallet. We draw
the line o o’ parallel with n u
and define the outer face of said pallet. In Fig.
21 we have not made any attempt to show the full outline
of the pallets, as they are delineated in precisely
the same manner as those previously shown.

We shall next describe the delineation of a club-tooth
escapement with pallets having equidistant locking
faces; and in Fig. 22 we shall show pallets with much
wider arms, because, in this instance, we shall derive
more of the impulse from the pallets than from the
teeth. We do this to show the horological student
the facility with which the club-tooth lever escapement
can be manipulated. We wish also to impress on
his mind the facts that the employment of thick pallet
arms and thin pallet arms depends on the teeth of
the escape wheel for its efficiency, and that he must
have knowledge enough of the principles of action to
tell at a glance on what lines the escapement was
constructed.

Suppose, for illustration, we get hold of a watch
which has thin pallet arms, or stones, if they are
exposed pallets, and the escape was designed for pallets
with thick arms. There is no sort of tinkering
we can do to give such a watch a good motion, except
to change either the escape wheel or the pallets.
If we know enough of the lever escapement to set about
it with skill and judgment, the matter is soon put
to rights; but otherwise we can look and squint, open
and close the bankings, and tinker about till doomsday,
and the watch be none the better.

CLUB-TOOTH LEVER WITH EQUIDISTANT LOCKING FACES.

In drawing a club-tooth lever escapement with equidistant
locking, we commence, as on former occasions, by producing
the vertical line A k, Fig. 22, and establishing
the center of the escape wheel at A, and with
the dividers set at 5” sweep the pitch circle
a. On each side of the intersection of
the vertical line A k with the arc a
we set off thirty degrees on said arc, and through
the points so established draw the radial lines A
b and A c.